The invention has particular utility in closing paint drainage holes in motor car bodies. Such apertures are formed more usually in the floor plan of a motor vehicle to allow excess paint to drain before the body is transferred to the paint oven where the paint is dried. The apertures can vary from quite a small size up to e.g. 90 mm diameter and they may be of a variety of shapes for instance circular, elliptical or oblong. Such plugs are commonly called "floor plugs" although not all such apertures are necessarily in the floor of the vehicle. Recent examples on floor plugs are described in British Pat. Nos. 1,466,563 and 1,466,564. In such plugs a body of sealant material is used between the plugs and the upper surface of the panel which flows at least to a limited extent when subjected to high temperature, normally in the paint oven. Sufficient sealant material is used for this to flow when heated to fill any irregularities in the panel region adjacent the plug, and in the adjacent plug surface, to ensure a complete seal.
While these plugs are generally successful in most applications, such plugs, particularly in the floor of the panel, are subjected to very considerable bombardment especially from rain water during travel of the motor vehicle and failures occur. The sealant or adhesive in such adhered plugs is restricted to the upper surface of the panel and normally between this surface and a flange portion of the plug which overlies the surface.
The invention is aimed at improving the adhesion of aperture plugs generally and particularly floor plugs, to provide a secure fixing without complicating the insertion procedure. The insertion procedure of floor plugs has to be rapid and efficient. The plugs have to be inserted by an operative while the car bodies are moving on a conveyor system.